1. Field of the Invention
The present invention relates to an optical fiber light source assembly and a manufacturing method thereof. More particularly, the optical fiber light source assembly includes a light source, a condenser lens, ferrule receptacle means for receiving an optical fiber ferrule, and a housing that assembles therewithin these components in that order from front to back. The manufacturing method permits the ferrule receptacle means to be adjustably moved in an axial direction of the housing.
2. Description of the Related Art
The coupler of a light source and an optical fiber is known to couple an optical fiber ferrule to an optical light assembly into which an optical fiber and a condenser lens are assembled.
As disclosed in U.S. Pat. Nos. 5,588,081 and 5,631,992, the inventors of this invention have proposed an optical fiber coupler device in which a gradient index (GRIN) lens converges a light beam from a light source, such as a can-type LED or a semiconductor laser, supported in a housing and an optical fiber supported by a ferrule is placed at a point of convergence of the light beam.
To enhance the coupling efficiency of such an optical fiber coupler device between the light source and the optical fiber, the light source, the condenser lens, and the center of the receiving end surface of the optical fiber have to be colinearly aligned (coaxial property) and the image of a point light source has to coincide with the center of the receiving end surface of the optical fiber (focusing). Failure to meet either of the two conditions lowers the coupling efficiency.
When a light emitting diode (LED) or a laser diode is used as a light source, variations in a light point (the position of the point light source) and the shape of a window plate give rise to the need for focusing. In a first method available for focusing, an optical fiber ferrule is fitted into a sleeve to the light source side, is brought into focus by sliding, and is then fixed with a setscrew, as described in the related art disclosed in each of the above-cited United States patents.
In a second method contemplated, a washer for adjusting spacing is placed between a light source side assembly and an optical fiber ferrule receptacle for focusing.
In a third method, an optical fiber ferrule receptacle is connected to a light source side assembly through a screw connection along the optical axis as a central axis to adjust the distance therebetween.
Since the diameter of the core of each optical fiber is as small as 9 .mu.m, it is occasionally required that the light point of the light source, the optical axis of the lens, and the central axis of the optical fiber core supported by the ferrule be aligned with each other. A light emitting device holder, a condenser lens holder and a ferrule holder are arranged and adjusted for precise optical axis alignment, and the coupling end surfaces of each holder are then fixed to each other through laser welding. Optical axis alignment is assured by measuring the output of the optical fiber coupled to the ferrule holder to determine a maximum output position.
The first method requires that each optical fiber ferrule be secured with a setscrew after focusing is performed on a ferrule by ferrule basis.
In the second method, the washer (annular ring spacer) for adjusting spacing is placed between the light source side assembly and the optical fiber ferrule receptacle to adjust the distance therebetween. The selection and mounting of the annular ring spacer are complicated, and the adjustment of the spacer needs to be performed in a stepwise fashion, and possibly causes the optical axis misalignment.
The third method also possibly gives rise to an offset between the central axes. For the alignment of the central axes, the light emitting device holder, the condenser lens holder and the ferrule holder may be handled separately, a reference surface of a ferrule end is defined in the ferrule holder, and one of the second and third methods may be used in combination. The alignment operation involved, however, becomes complex and needs an expensive aligning welding machine.